Influenza A H7N9 virus is one of a subgroup of influenza viruses that normally circulate among birds, and is endemic in the Asian domestic chicken population. Until recently, this influenza virus had not been seen in humans. A novel reassortant avian influenza A H7N9 virus associated with severe human infection was first reported in early 2013 in China. (See, e.g., Gao et al. (2013) NEJM 368:1888-1897.) The initial outbreak of this avian influenza virus infection in humans during the spring of 2013 resulted in 132 confirmed cases and 44 deaths. It is believed that most of the infected individuals contracted the virus through direct contact with infected poultry.
To date, no sustained human-to-human transmission of avian influenza A H7N9 virus has been observed. However, studies using ferrets, which like humans infect one another through coughing and sneezing, showed that one influenza A H7N9 virus strain isolated from humans can transmit ferret-to-ferret through respiratory droplets.
Of significant concern is the pandemic potential of this virus. As influenza viruses constantly change, the possibility for avian H7N9 influenza virus becoming transmissible between humans, and that such transmission could result in a global pandemic cannot be excluded. If H7N9 influenza viruses acquire the ability to transmit efficiently from human to human, a worldwide outbreak may occur, as humans lack protective immune responses to these types of viruses. Therefore, a need exists for novel therapies effective at treating and preventing influenza A H7N9 virus infections in humans.
The present invention meets this need and provides other benefits for the treatment of avian influenza A H7N9 virus infection.